Unable to send message using SendMessage

Hello this is my first posting here. I have read numerous postings but this is my first contribution.

I am trying to use Sendmessage to send a string of text from one application to another. I have created a sandbox to work out the details.

I have used the “Notepad” example and I have gotten that to function.

This is what I have that works.

Code:

---

Public Class Xnutalk

 
    Private Declare Function SendMessageByString Lib "user32.dll" Alias "SendMessageA"_
    (ByVal hwnd As IntPtr, ByVal uMsg As Int32, ByVal wParam As IntPtr, ByVal lParam As String) As Integer

    Private Const WM_SETTEXT As Int32 = &HC
 
    Private Const WM_GETTEXTLENGTH As Int32 = &HE

    Private Declare Function FindWindow Lib "user32" Alias "FindWindowA"_
    (ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr

    Private Declare Function FindWindowEx Lib "user32.dll" Alias "FindWindowExA"_
    (ByVal hWnd1 As IntPtr, ByVal hWnd2 As IntPtr, ByVal lpsz1 As String, ByVal lpsz2 As String) As IntPtr


    Public Function GetHandle(ByVal ClassName As String) As IntPtr

        Dim hwnd As IntPtr = FindWindow(ClassName, Nothing)

        hwnd = FindWindowEx(hwnd, IntPtr.Zero, Nothing, "Xnu talk client")

        If (Not hwnd.Equals(IntPtr.Zero)) Then
            Return hwnd
        Else
            Return IntPtr.Zero
        End If
    End Function


    Sub SetNewText(ByVal hwnd As IntPtr, ByVal txt As String)
        If (Not hwnd.Equals(IntPtr.Zero)) Then
           
            Call SendMessageByString(hwnd, WM_SETTEXT, IntPtr.Zero, txt)
        End If
    End Sub


    Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim khwnd As IntPtr
 
        khwnd = GetHandle("xnutalk client")

        SetNewText(khwnd, "Hello")

 
    End Sub

---

Now what I am trying to do is modify it so instead of changing the title bar, it adds the text, in the example “Hello”, to a TextBox inside the Window. I have not been able to figure that out.

I have tried many permutations of this and I think I am staring at trees looking for a forest.

Here is what I have tried:

Code:

---


Public Class Xnutalk

 
    Private Declare Function SendMessageByString Lib "user32.dll" Alias "SendMessageA"_
    (ByVal hwnd As IntPtr, ByVal uMsg As Int32, ByVal wParam As IntPtr, ByVal lParam As String) As Integer

    Private Const WM_SETTEXT As Int32 = &HC
 
    Private Const WM_GETTEXTLENGTH As Int32 = &HE

    Private Declare Function FindWindow Lib "user32" Alias "FindWindowA"_
    (ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr

    Private Declare Function FindWindowEx Lib "user32.dll" Alias "FindWindowExA"_
    (ByVal hWnd1 As IntPtr, ByVal hWnd2 As IntPtr, ByVal lpsz1 As String, ByVal lpsz2 As String) As IntPtr


    Public Function GetHandle(ByVal ClassName As String) As IntPtr

        Dim hwnd As IntPtr = FindWindow(ClassName, Nothing)

        hwnd = FindWindowEx(hwnd, IntPtr.Zero, Nothing, "chatbox")

        If (Not hwnd.Equals(IntPtr.Zero)) Then
            Return hwnd
        Else
            Return IntPtr.Zero
        End If
    End Function


    Sub SetNewText(ByVal hwnd As IntPtr, ByVal txt As String)
        If (Not hwnd.Equals(IntPtr.Zero)) Then
           
            Call SendMessageByString(hwnd, WM_SETTEXT, IntPtr.Zero, txt)
        End If
    End Sub


    Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim khwnd As IntPtr
 
        khwnd = GetHandle("xnutalk client")

        SetNewText(khwnd, "Hello")

 
    End Sub

---

Where chatbox is the name of the box in question.

Does anyone have any ideas?

Man I hope someone can assist me with this, I have been beating my head against a wall for some time now. I just cannot seem to understand why FindWindowEX cannot seem to find any element within xnutalk client.

I may just have so little understanding as I do not know what I should even be asking.

I understand from examples that FindwindowEX should find an element within the Findwindow window that is found (assuming there is one). But this is not happening.

FindWindowEx is calling GetWindowText internally and compares the result to the parameter you specified as window title.

GetWindowText is looking at a predefined address in the process memory for the name of the window. If the name is not there, FindWindowEx is not receiving anything (at least not a match) and so the functionality is kind of broken. This is done on purpose so that your program will not hang if the other program is not responding.

Not every third party control conforms to the convention to store it's title where it is supposed to for example java, flash, qwidget...